An axial flow rotary machine, such as a gas turbine engine for an aircraft, includes a compression section, a combustion section and a turbine section. A flow path for hot working medium gases extends axially through the sections of the engine. The flow path for hot gases is generally annular in shape.
As the working medium gases are flowed along the flow path, the gases are compressed in the compression section causing the temperature and pressure of the gases to rise. The hot, pressurized gases are burned with fuel in the combustion section to add energy to the gases. These gases are expanded through the turbine section to produce useful work and thrust.
The engine has a rotor assembly in the turbine section which is adapted by a rotor disk and blades which extend outwardly therefrom to receive energy from the hot working medium gases. The rotor assembly extends to the compression section. The rotor assembly has compressor blades extending outwardly across the working medium flow path. The high energy working medium gases in the turbine section drive the rotor assembly about its axis of rotation. The compressor blades rotate with the rotor assembly and drive the incoming working medium gases rearwardly, compressing and heating the gases prior to the gases entering the combustion chamber.
The stator assembly includes a plurality of bearing compartments. Each bearing compartment has at least one bearing for supporting the rotating shaft of the rotor assembly from the stator assembly. The bearing in the bearing compartment is supplied with a lubricating fluid, such as oil, for lubricating its surfaces. A seal assembly extends between the rotating shaft and the bearing compartment to block the leakage of oil from the bearing compartment and the leakage of hot working medium gases into the bearing compartment.
One example of a seal assembly for such a bearing compartment is shown in U.S. Pat. No. 4,406,459 issued to Davis and Sidat entitled "Oil Weepage Return for Carbon Seal Plates" which is assigned to the assignee of this application. In this construction, the seal assembly has a seal plate which is rotatably attached to the rotor shaft. A seal element, typically formed of carbon, is supported by the stator assembly and is urged against the seal plate to block the leakage of oil out of the compartment and the leakage of working medium gases into the compartment. Oil is supplied to the location of abutting contact between the seal plate the seal element to lubricate these rubbing surfaces.
Oil supplied to these surfaces may flow from the seal assembly out into the region between the seal assembly and the rotor shaft. An oil return passage 58 in the seal plate provides a conduit for returning the oil to the bearing compartment. Rotation of the seal plate about the axis of the engine exerts a radial force on oil in the return passage and forces the oil radially outwardly through the passages.
Occasionally, oil leaking from the bearing compartment will migrate through cavities between the rotor shaft and the seal element into the interior of the engine. The oil may reach a location where it accumulates in insulation or is trapped in other areas of the engine. This creates a potential for fires should the oil come in contact with hot working medium gases which contain oxygen and remain there at a high enough temperature for a sufficient length of time to cause ignition.
The above art notwithstanding, scientists and engineers working under the direction of applicant's assignee have sought to further block the migration of oil from the bearing compartment into the interior of the rotary machine.